CN113145905A - Measuring, predicting and optimizing method and device for milling cutter marks on top surface of engine cylinder block - Google Patents
Measuring, predicting and optimizing method and device for milling cutter marks on top surface of engine cylinder block Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23C—MILLING
- B23C3/00—Milling particular work; Special milling operations; Machines therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
- B23Q17/20—Arrangements for observing, indicating or measuring on machine tools for indicating or measuring workpiece characteristics, e.g. contour, dimension, hardness
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- G—PHYSICS
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- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
- G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
Abstract
The invention discloses a method and a device for measuring, predicting and optimizing milling cutter marks on the top surface of an engine cylinder body, wherein the method comprises the following steps: preprocessing the point cloud data of the top surface of the cylinder body obtained by high-definition measurement, eliminating abnormal outliers, filtering the point cloud data, extracting the characteristics of the tool marks in the high-pass signal, and defining the three-dimensional evaluation index of the tool marks according to the characteristics; according to the milling characteristics of the top surface of the engine cylinder body, the influence caused by the inclination of a main shaft, the abrasion of a cutter and the jumping of the cutter is comprehensively considered, and the physical modeling is carried out on the forming process of the cutter mark; predicting the quality of the milling surface according to the physical model of the tool marks, calculating the three-dimensional evaluation index value of the tool marks generated under the condition of specific process parameters, establishing a process parameter multi-objective optimization model according to the three-dimensional evaluation index value, and obtaining the optimal process parameter scheme suitable for milling the top surface of the engine cylinder block by solving the optimization model. According to the invention, by defining and accurately predicting the characteristic indexes of the tool marks on the milling surface, the milling process parameters of the top surface of the engine cylinder body are effectively optimized, so that the milling processing quality of the top surface of the engine cylinder body is improved.
Description
Technical Field
The invention relates to surface machining of an engine cylinder block, in particular to a method for measuring, predicting and optimizing milling cutter marks on the top surface of the engine cylinder block.
Background
The engine cylinder block is one of the core components of the engine, the processing precision of the key surface of the engine cylinder block directly influences the service performance of the automobile engine, wherein the top surface of the engine cylinder block is used as a joint surface with an engine cylinder cover, and the milling processing quality of the engine cylinder block directly influences the sealing performance of the engine. In the milling process of the top surface of the engine cylinder block, due to the influences of factors such as main shaft inclination, cutter abrasion, cutter bounce and the like, a tool mark morphology error between a macroscopic flatness error and a microscopic roughness error is often generated, and the morphology characteristics of the tool mark morphology error directly influence the waviness error of a processing plane, so that the sealing performance of an engine product is determined. By processing and mining high-definition measurement point cloud data of the top surface of the engine cylinder body, establishing a tool mark characteristic evaluation index, carrying out physical modeling on a milling tool mark forming mechanism, predicting milling surface tool mark characteristics, optimizing milling process parameters according to the tool mark characteristic evaluation index, reducing milling waviness errors of the top surface of the cylinder body, and being an important ring for improving the product performance of the engine.
Through the search of the prior art documents, the influence of plane milling parameters, dry milling and cutter abrasion on the surface roughness and surface defects of parts is researched by the method combining a machining experiment and finite element simulation in a paper "titanium alloy TB6 milling surface roughness and surface defect research" ("aeronautical manufacturing technology" 2017, 5 th, pages 60-66). The method comprehensively considers the influence of process parameters, lubrication conditions, temperature distribution and cutter abrasion on the part in the plane milling process, and analyzes the formation rule of the surface roughness and the surface defects, however, the method focuses on the processing experimental design and the establishment of a finite element simulation model, and the method lacks discussion and research on the physical mechanism of the part surface errors and the defect formation. In addition, although the method pays attention to the surface roughness of a microscopic level and the surface defects of a macroscopic level, the waviness error between the microscopic level and the macroscopic level is ignored, and the three-dimensional morphology characteristic rules of the waviness error levels such as tool marks and the like are not considered, so that the method cannot be effectively applied to surface quality improvement of milling of the top surface of the engine cylinder block.
Further retrieval finds that in the thesis of extraction and research of the milling surface waviness characteristics of the aeronautical structural member (surface technology 2016, volume 45, stage 9, page 154-162), the Wang Hongle and the like, a method combining spectral analysis and wavelet analysis is provided by taking the milling surface of the aeronautical structural member as an object, and characteristic extraction and evaluation are carried out on the surface waviness errors of the part. The method comprises the steps of carrying out spectrum analysis on the comprehensive surface appearance of the part milling surface, determining the frequency band range of effective information of each surface component, decomposing original surface appearance characteristics by adopting wavelets, decomposing information containing different frequency components onto frequency bands which are not overlapped with each other, calculating each approximation coefficient and a wavelet coefficient, and reconstructing the effective frequency bands to extract different frequency components of the surface appearance characteristics and further obtain appearance characteristic information of surface waviness. The method provides a visual reference basis for controlling and reducing the milling surface waviness of the part, however, the method still ignores the mechanism of forming the waviness error, and does not consider the influence of actual factors such as main shaft inclination, cutter abrasion and cutter jumping on the waviness of the machined surface of the part from the physical essential angle, so that the method has certain limitation on the prediction of the waviness error and the optimization of milling process parameters.
Disclosure of Invention
1. Objects of the invention
The invention aims to provide a method for measuring, predicting and optimizing milling cutter marks on the top surface of an engine cylinder block.
2. The technical scheme adopted by the invention
The invention provides a method for measuring, predicting and optimizing milling cutter marks on the top surface of an engine cylinder block, which comprises the following steps of:
step 1: preprocessing high-definition point cloud data of the top surface of the engine cylinder body, eliminating abnormal outlier data points, filtering the point cloud data, extracting tool mark characteristics in a high-pass signal, and performing tool mark conversion;
step 2: defining three specific three-dimensional evaluation indexes of tool mark characteristics according to three-dimensional tool mark appearance data obtained by point cloud filtering and tool mark conversion extraction;
and step 3: comprehensively considering the influences of main shaft inclination, cutter abrasion and cutter jumping commonly seen in the milling process of the top surface of the engine cylinder block, and establishing a cutter mark forming physical model;
and 4, step 4: predicting the quality of the milling surface according to a cutter mark forming physical model, calculating a three-dimensional evaluation index numerical value of cutter marks generated under the condition of specific process parameters, and establishing a milling process parameter multi-target optimization model according to the three-dimensional evaluation index numerical value;
and 5: and solving the multi-objective optimization model to obtain an optimal process parameter scheme suitable for milling the top surface of the engine cylinder body, and accordingly milling the top surface of the engine cylinder body.
3. Advantageous effects adopted by the present invention
(1) In step 1 of the invention, the filtering method is a plate splicing wave method, and the point cloud data is decomposed into low-frequency coefficients and high-frequency coefficients with different scales. Compared with the traditional Gaussian filtering and wavelet methods, the method has the greatest difference that the original point cloud image can be divided into a series of 4 multiplied by 4 splicing blocks, and the optimal combination scheme is selected from various combination schemes according to the geometric characteristics of the point cloud image, so that the problem that multiple holes on the top surface of the cylinder body are not connected with each other is effectively avoided
(2) In step 4 of the invention, variables of the optimization model are milling process parameters which can be accurately controlled and adjusted by the numerical control machine tool, including the rotating speed of the main shaft, the feeding speed, the axial cutting depth and the number of cutter teeth of the disc milling cutter.
(3) In step 5 of the method, the multi-objective function of the optimization model can be simplified into a single objective function optimization problem by weighting each objective, and the solution can be rapidly and effectively carried out through a genetic algorithm, so that an optimal milling process parameter scheme is obtained and used for guiding the milling processing of the top surface of the engine cylinder block.
(4) The invention sets up a cutter mark forming physical model suitable for the milling process of the top surface of the engine cylinder block from the internal mechanism of cutter mark formation, and restores the real physical state of the interaction between the cutter and the workpiece, so that the invention is a cutter mark characteristic prediction method based on a physical analysis model, rather than a prediction method completely depending on experiments or simulation, and has stronger theoretical persuasion and prediction accuracy;
(5) the invention comprehensively considers the effects of factors such as main shaft inclination, cutter abrasion, cutter bounce and the like, deeply researches the evolution rule of the edge motion trail of the disc milling cutter along with the change of milling process parameters, calculates the influence effect of the cutter abrasion and the bounce on the thickness of undeformed cuttings, ensures that the cutter mark characteristic prediction result is more accurate, and provides a solid theoretical basis for the optimization of the milling process parameters of the top surface of the engine cylinder body.
(6) The invention provides innovative evaluation indexes for high-definition point cloud data containing tool mark characteristics, the tool mark morphological characteristics are evaluated from three mutually perpendicular directions according to the process characteristics of milling processing of the top surface of an engine cylinder body, and each index can be obtained through calculation of a tool mark forming physical model provided by the invention and forms mapping association of mathematical analysis with each milling process parameter, so that technical reference is provided for similar research, and meanwhile, the invention also has important engineering practical value.
Drawings
FIG. 1 is a schematic diagram of the flow of the milling tool marks of the top surface of the engine cylinder block in the invention at each stage of predicting and optimizing;
FIG. 2 is a schematic view of the tool mark conversion principle of the present invention;
FIG. 3 is a schematic diagram illustrating the definition of the evaluation index of tool mark characteristics according to the present invention;
FIG. 4 is a schematic view of the present invention showing the contact between the disc cutter and the workpiece when the spindle is tilted;
FIG. 5 is a schematic diagram of three runout conditions of the cutter teeth of the disc cutter of the present invention;
FIG. 6 is a schematic illustration of the impact of undeformed chips of the present invention as affected by spindle tilt and tool wear;
FIG. 7 is a schematic illustration of the effective cutting area of a single worn tooth in accordance with the present invention.
In the figure:
1 is the average tool mark peak valley difference expressed as hd；
2 is the average tool mark wavelength, expressed as sλ；
3 is a single tool mark height fluctuation, expressed as hf；
4 is the actual angle between the cutting edge of the cutter tooth of the disc cutter and the ideal horizontal line and is expressed as
5 is the angle of inclination of the central axis of the main shaft from the ideal vertical direction, expressed as
6 is the actual included angle between the bottom side of the cross section A-A of the middle shaft of the i-th undeformed chip and an ideal horizontal line and is expressed as gammai。
Detailed Description
The technical solutions in the examples of the present invention are clearly and completely described below with reference to the drawings in the examples of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, are within the scope of the present invention.
The present invention will be described in further detail with reference to the accompanying drawings.
Example 1
As shown in fig. 1 to 7, in this embodiment, the method for predicting and optimizing the milling tool mark based on the engine block top surface comprises the following steps:
step 1: the method comprises the following steps of preprocessing original three-dimensional point cloud data of the top surface of an engine cylinder body obtained by a high-definition measuring means, wherein the preprocessing comprises three operations of outlier rejection, filtering and tool mark conversion. For cylinder workpieces of known models, the nominal height from a measuring plane to a reference plane is a known determined value, the deviation value of the measured actual height and the nominal height can also be obtained by subtracting the nominal height from the measuring plane, a critical threshold value P is preset for the deviation, and if the deviation value of any data point is greater than P, the data point is regarded as an outlier for rejection. Picking out outliersAfter removing, filtering the point cloud data by using a plate splicing wave method, decomposing the point cloud data into low-frequency coefficients and high-frequency coefficients with different scales, intercepting a high-pass signal as surface morphology error data, wherein the cutoff wavelength is 0.8mm and is expressed as lambdaf. Because the tool marks generated by actual processing are cycloid-shaped arcs, the intuitive judgment and accurate calculation of each index are not facilitated, and therefore, certain conversion needs to be carried out on the horizontal and vertical coordinates of the data points, so that each tool mark is converted into a mutually parallel straight line. As shown in fig. 2, arc line
Representing any one tool mark, feeding a disc milling cutter with the diameter of R along the X-axis direction at the speed of f, wherein the rotating speed of a main shaft is omega, and the initial coordinate of the center of the disc milling cutter is set as [ X ]O,yO]When the knife teeth reach the arc line
The time of any point B is tBThe coordinates of the point B can be expressed as
Through the tool mark conversion, the coordinate of the corresponding point B' of the point B on the converted tool mark can be expressed as
The Z-axis coordinate of each data point remains unchanged during the tool mark transformation.
Step 2: defining three-dimensional evaluation indexes of the characteristics of the three tool marks according to three-dimensional tool mark shape data obtained by point cloud filtering and tool mark conversion extraction, wherein the three-dimensional evaluation indexes specifically comprise average tool mark peak-valley difference which is expressed as hdThe method is used for describing the peak-valley fluctuation condition of the integral tool mark in the direction vertical to the top surface of the cylinder body; average tool mark wavelength, expressed as sλFor describing the spacing of adjacent tool marks in the feed direction of the disc cutter(ii) a condition; single line tool mark height fluctuation, denoted as hfThe height fluctuation of the single tool mark in the direction perpendicular to the feeding direction of the disc milling cutter is described. As shown in FIG. 3, considering a series of consecutive adjacent tool marks within the sample area, numbered sequentially as {1,2, …, s }, the average tool mark peak-to-valley difference can be expressed as
Wherein z isiRepresents the Z-axis coordinate set of all data points on the ith tool trace. Average tool mark peak valley difference hdThe effect on the waviness error is most direct and significant, and should be kept as small as possible.
After the tool mark conversion, all the tool marks are perpendicular to the feeding direction (X-axis direction), so that the X-axis coordinate coordinates corresponding to each tool mark peak can be sequentially expressed as { X }1,x2,…,xsThe average tool mark wavelength can be expressed as
Average tool mark wavelength sλWill directly influence the cut-off wavelength lambdafIs chosen such that, in order to guarantee an accurate evaluation of the waviness error, the difference λ between the two wavelengthsf-sλThe larger should be kept the better.
For a single tool mark, the peak height of the tool mark fluctuates in the Y-axis direction due to factors such as the inclination of the main shaft, and the fluctuation of the height of the single tool mark can be expressed as
Wherein zi|x＝xiAnd represents the Z-axis coordinate set of all data points on the peak of the ith tool mark. Single line of tool mark height fluctuation hfThe sealing performance of the engine product is adversely affected, and the smaller the sealing performance, the better the sealing performance.
And step 3: and comprehensively considering the influences of main shaft inclination, cutter abrasion and cutter jumping commonly seen in the milling process of the top surface of the engine cylinder block, and establishing a cutter mark forming physical model. Considering spindles with slight inclination
The face milling process of (1), as shown in fig. 4, can calculate the actual rotary cutting diameter of the disc milling cutter due to the inclination of the spindle to be
The included angle between two adjacent cutter teeth of the disc milling cutter is recorded as k, so that the cutting time t at any cutting time can be further obtainedcThe cutter mark track formed by the ith cutter tooth is
The universal disc cutter tooth comprises a cutting edge primarily responsible for material removal and a finishing edge primarily responsible for finishing the machining plane, noting that the actual included angle between the cutting edge and the ideal horizontal line is
Feed per tooth of fzThe undeformed chip thickness is then denoted tuc＝fz cosφa. Considering that the possible run-out errors of any ith cutter tooth in the axial direction, the radial direction and the rotating direction in the installation process are respectively expressed as epsilonai，εriAnd betaiThe effect of tool runout on the actual material removal can be expressed as shown in fig. 5
Wherein a'p_iRepresenting the actual axial cutting depth, t ', of the ith cutter tooth influenced by cutter runout'uc_iThe actual undeformed chip thickness of the ith tooth, as affected by tool runout, is shown.
The ideal undeformed cuttings are usually in a form of thick middle and thin two ends under the influence of the inclination of the main shaft, as shown in fig. 6(1), the ith undeformed cuttings are formed by the fact that the swept surface of the ith cutter tooth is wrapped by the swept surface of the ith-1 cutter tooth and the swept surface of the ith cutter tooth, the section A-A is taken along the central axis of the cuttings, and the actual included angle between the bottom edge of the section and the ideal horizontal line is recorded as gammai. Considering the case of wiper blade wear of the tool, as shown in fig. 6(2), including local tipping and flank wear, respectively, reduces the actual effective cutting area of the cutter teeth, thereby affecting the tool mark characteristics. By high wear h of the whole bladeiAs shown in fig. 7, the analytical formula for the average tool mark peak-valley difference can be obtained as
Wherein α is the angle between adjacent cutting and wiper edges.
The total cutter tooth number of the disc milling cutter is recorded as N, and the analytical formula for obtaining the average cutter mark wavelength is
Meanwhile, the analytic formula for obtaining the height fluctuation of a single tool mark is
Wherein a iseThe radial cutting depth of the milling process is represented, and the size of the radial cutting depth is determined by the feed path, the tool geometry and the workpiece surface continuity, and can be obtained by calculation according to the actual machining condition.
And 4, step 4: and predicting the quality of the milling surface according to the cutter mark forming physical model, calculating a three-dimensional evaluation index value of the cutter mark generated under the condition of specific process parameters, and establishing a milling process parameter multi-target optimization model according to the three-dimensional evaluation index value. The optimization model specifically comprises the following steps:
the objective function is:
the constraint conditions are as follows:
wherein omegastAnd ΩfiRespectively represents the lower limit and the upper limit of the rotating speed of the main shaft suitable for milling of the machine tool, ap_lim(omega) represents the chatter-free limit axial cutting depth corresponding to the main shaft drilling speed omega, N*Representing the maximum number of teeth that the disc cutter can accommodate.
And 5: aiming at the multi-objective function of the optimization model, the model can be simplified into a single objective function optimization problem by weighting each objective, and particularly, the objective function can be simplified into a single objective function optimization problem
Wherein, w1,w2And w3Respectively represent the weight corresponding to each target and satisfy w1+w2+w 31. In the invention, the three weights are respectively 0.6, 0.15 and 0.25.
The model can be solved quickly and efficiently by genetic algorithms. The main flow of the adopted genetic algorithm is as follows: (1) initializing a population by taking a milling process parameter scheme meeting constraint conditions as an individual; (2) calculating various tool mark characteristic evaluation indexes under the condition of specific process parameters by using the tool mark forming physical model, so as to calculate the fitness function value of each individual; (3) setting a roulette wheel selection operator according to the fitness value to obtain enough 'excellent' individuals; (4) carrying out random cross substitution on chromosomes of 'excellent' individuals according to a preset cross rule; (5) randomly carrying out partial variation on individual chromosomes in the population according to a preset variation rule to finally obtain a new generation of population; (6) and (3) judging whether a termination condition is met or not according to the variation trend of the fitness, if so, stopping iteration, and if not, repeating the steps (1) to (5) until the termination condition is met, namely, the maximum fitness is kept at the same level for more than one thousand generations, and then, iteratively solving to reach the termination condition, wherein the optimal individual in the obtained population is used as an optimal milling process parameter scheme.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (9)
1. A measuring, predicting and optimizing method for milling cutter marks on the engine cylinder body top surface is characterized by comprising the following steps:
step 1: preprocessing high-definition point cloud data on the top surface of an engine cylinder body, removing abnormal outlier data points, filtering the point cloud data, extracting tool mark characteristics in a high-pass signal, and converting horizontal and vertical coordinates of the data points to convert all tool marks into parallel straight lines;
step 2: defining three specific three-dimensional evaluation indexes of tool mark characteristics according to three-dimensional tool mark shape data obtained by point cloud filtering and tool mark conversion extraction, wherein the three-dimensional evaluation indexes comprise average tool mark peak-valley difference and are used for describing the peak-valley fluctuation condition of the whole tool mark in the direction vertical to the top surface of the cylinder body; the average tool mark wavelength is used for describing the distribution of the distance between every two adjacent tool marks along the feeding direction of the disc milling cutter; the height fluctuation of the single tool mark is used for describing the height fluctuation condition of the single tool mark in the direction vertical to the feeding direction of the disc milling cutter;
and step 3: comprehensively considering the influences of main shaft inclination, cutter abrasion and cutter jumping commonly seen in the milling process of the top surface of the engine cylinder block, and establishing a cutter mark forming physical model;
and 4, step 4: predicting the quality of the milling surface according to a cutter mark forming physical model, calculating a three-dimensional evaluation index numerical value of cutter marks generated under the condition of specific process parameters, and establishing a milling process parameter multi-target optimization model according to the three-dimensional evaluation index numerical value;
and 5: and solving the multi-objective optimization model to obtain an optimal process parameter scheme suitable for milling the top surface of the engine cylinder body, and accordingly milling the top surface of the engine cylinder body.
2. The engine block top surface milling tool mark measurement prediction and optimization method according to claim 1, characterized in that:
step 1: preprocessing original three-dimensional point cloud data of the top surface of the engine cylinder body obtained by a high-definition measuring means, wherein the preprocessing comprises three operations of outlier rejection, filtering and tool mark conversion;
step 1.1, for cylinder body workpieces with known models, the nominal height from a measuring plane to a reference plane is a known determined value, the actual height obtained by measurement and the deviation value of the nominal height are obtained by subtracting the actual height and the nominal height, a critical threshold value P is preset for the deviation, and if the deviation value of any data point is greater than P, the data point is regarded as an outlier for rejection; after outlier rejection is completed, filtering the point cloud data by using a plate splicing wave method, decomposing the point cloud data into low-frequency coefficients and high-frequency coefficients of different scales, intercepting a high-pass signal as surface morphology error data, and expressing a cutoff wavelength as lambdaf；
Step 1.2, converting the horizontal and vertical coordinates of the data points to convert all tool marks into mutually parallel straight lines; arc line
Representing any one tool mark, feeding a disc milling cutter with the diameter of R along the X-axis direction at the speed of f, wherein the rotating speed of a main shaft is omega, and the initial coordinate of the center of the disc milling cutter is set as [ X ]O，yO]When the knife teeth reach the arc line
The time of any point B is tBThen the coordinates of point B are expressed as
Through the tool mark conversion, the coordinate of the corresponding point B' of the point B on the converted tool mark is expressed as
The Z-axis coordinate of each data point remains unchanged during the tool mark transformation.
3. The engine block top surface milling tool mark measurement prediction and optimization method according to claim 1, characterized in that:
step 2: according to three-dimensional tool mark appearance data obtained by point cloud filtering and tool mark conversion extraction, three tool mark characteristic three-dimensional evaluation indexes including average tool mark peak-valley difference h are defineddAverage tool mark wavelength sλSingle line of tool mark height fluctuation hf(ii) a Considering a series of continuous adjacent tool marks in the sampling area, which are sequentially numbered as {1, 2.., s }, the average tool mark peak-valley difference is expressed as
Wherein z isiA set of Z-axis coordinates representing all data points on the ith tool mark; average tool mark peak valley difference hdThe most direct and significant impact on waviness errors;
after the tool mark conversion, all the tool marks are perpendicular to the feeding direction, namely the X-axis direction, so that the X-axis coordinate coordinates corresponding to the wave crests of the tool marks are sequentially expressed as { X }1，x2，...，xsDenotes the average tool mark wavelength as
Average tool mark wavelength sλWill directly influence the cut-off wavelength lambdafSelecting;
for a single tool mark, the peak height of the tool mark fluctuates in the Y-axis direction due to factors such as the inclination of the main shaft, and the fluctuation of the height of the single tool mark is expressed as
Wherein zi|x＝xiAnd represents the Z-axis coordinate set of all data points on the peak of the ith tool mark.
4. The engine block top surface milling scar measurement prediction and optimization method of claim 1, characterized by step 3: establishing a cutter mark forming physical model; with slightly-inclined main shaft
Face milling with a disc cutter actual rotary cutting diameter due to spindle inclination of
Recording the interval included angle of two adjacent disc milling cutter teeth as K to obtain the cutting time t at any timecThe cutter mark track formed by the ith cutter tooth is
5. The engine block top surface milling tool mark measurement prediction and optimization method according to claim 4, characterized in that:
the disc cutter tooth comprises a cutting edge for material removal and a wiper edge for trimming the machining plane, noting the actual distance between the cutting edge and the ideal horizontal lineIncluded angle of
Feed per tooth of fzThe undeformed chip thickness is then denoted tuc＝fzcosφa(ii) a Considering that the jumping errors of any ith cutter tooth in the axial direction, the radial direction and the rotating direction exist in the installation process, and are respectively expressed as epsilonai，εriAnd betaiThe effect of tool runout on actual material removal is expressed as
Wherein a'p_iRepresenting the actual axial cutting depth, t ', of the ith cutter tooth influenced by cutter runout'uc_iThe actual undeformed chip thickness of the ith tooth, as affected by tool runout, is shown.
6. The engine block top surface milling tool mark measurement prediction and optimization method according to claim 5, characterized in that:
under the influence of the inclination of the main shaft, the undeformed cuttings are generally in the shapes of thick middle and thin two ends, the ith undeformed cuttings are formed by the i-1 th cutter tooth swept surface and the ith cutter tooth swept surface in an interlaced mode, the section A-A is taken along the central axis of the cuttings, and the actual included angle between the bottom edge of the section and an ideal horizontal line is recorded as gammai(ii) a The condition of the sharpening and the grinding of the cutter is considered, the condition comprises local tipping and side surface abrasion, and the actual effective cutting area of the cutter tooth can be reduced, so that the cutter mark characteristics are influenced; by high wear h of the whole bladeiThe analytical formula for obtaining the average tool mark peak-valley difference is as follows
Wherein alpha is an included angle between adjacent cutting edges and the smoothing edge;
the total cutter tooth number of the disc milling cutter is recorded as N, and the analytical formula for obtaining the average cutter mark wavelength is
Meanwhile, the analytic formula for obtaining the height fluctuation of the single tool mark is
Wherein a iseThe radial cutting depth of the milling process is represented, and the size of the radial cutting depth is determined by the feed path, the tool geometry and the workpiece surface continuity together and is calculated according to the actual machining condition.
7. The engine block top surface milling tool mark measurement prediction and optimization method according to claim 1, characterized by step 4: predicting the quality of the milling surface according to a cutter mark forming physical model, calculating a three-dimensional evaluation index numerical value of cutter marks generated under the condition of specific process parameters, and establishing a milling process parameter multi-target optimization model according to the three-dimensional evaluation index numerical value; the optimization model specifically comprises the following steps:
the objective function is:
the constraint conditions are as follows:
wherein omegastAnd ΩfiRespectively represents the lower limit and the upper limit of the rotating speed of the main shaft suitable for milling of the machine tool, ap_lim(omega) represents the chatter-free limit axial cutting depth corresponding to the main shaft drilling speed omega, N*Representing the maximum number of teeth that the disc cutter can accommodate.
8. The engine block top surface milling tool mark measurement prediction and optimization method according to claim 1, characterized in that:
and 5: aiming at a multi-objective function of an optimization model, the model is simplified into a single objective function optimization problem by weighting each objective, and particularly, the objective function is simplified into a single objective function optimization problem
Wherein, w1，w2And w3Respectively represent the weight corresponding to each target and satisfy w1+w2+w31. In the invention, the three weights are respectively 0.6, 0.15 and 0.25.
9. The device for measuring, predicting and optimizing the milling cutter mark on the top surface of the engine cylinder block comprises a memory and a processor, wherein the memory stores a computer program and is characterized in that; the processor, when executing the computer program, realizes the method steps of any of claims 1-8.
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